Perception Final Exam

Is your skin equally sensitive to detail all across your body? Describe a demonstration that supports your answer.

Supposed to show: Receptive field size--fingers have smaller receptive field, but they are overrepresented in the somatosensory cortex → similar to cortical magnification (fovea overrepresented in the visual field) (fingers and lips have higher density of receptors) Higher density of receptors = a smaller and denser receptive field

Describe the relationship between visual angle, object size, and distance.

The angle formed at the eye by rays from the extremities of an object viewed. (the top of an image and bottom all focus to a point on retina through an angle -Taller the image the larger the visual angle and the closer it is to us.

Vestibular System

- 3 Canals filled with liquid; corresponds to your sense of gravity, linear acceleration, -The motion of liquid in ear refers to the motion of the head

What are the functions of the different parts of the eye? (cornea, pupil, lens, retina)

- Function of pupil is to adjust light into the eye; pupil contracts or expands depending on how much light we want to let into the eye -The cornea and the lens both focus light entering the eye. The lens, unlike the cornea, has the ability to change shape to adjust to the distance of the object from the eye. If an object is closer to the eye, the lens contracts, becoming thicker in order to focus the light on the retina and make the image clearer. The purpose of the retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition.

What are the dominant brain waves associated with the different stages of sleep? What occurs during REM sleep?

- Stage 1: Theta Waves light sleep , muscle activity slows 4- 7 HZ; Stage 2: Beta Waves 13-30 engaged; Stage 3: Deep sleep; .5- 3 HZ Delta Waves; Stage 4: Very deep sleep; delta waves. Stage 5: Gamma Waves highly alert31-120 HZ; REM Sleep is characterized by rapid eye movement and you dream

How does virtual reality perception differ from real world perception? What are some ways in which virtual reality technology can help us study perception?

- VR as a research tool -Manipulate the environment ○ Create situaitons that are difficult or impossible to create in a real lab -Manipulate visual orientation cues ○Applications -Health -Defense -Recovery -Education -Sports training -Orientation experiments -Study binocular rilvary and the HMD

Discuss reasons why object recognition is challenging for computer vision systems.

-Ambiguity:different images produce same image in the visual system -Viewpoint Invariance: Looking at things from different angles, the object looks different -Blur: blurry objects are harder to identify -Occlusion: objects that are partially covered are harder to identify

What are two binaural cues that help us estimate the source of a sound? How is the frequency of sound related to the reliability of each of the binaural localization cues.

-Binaural cues: Azimuth (left & right) -If sound is directly in front of subject, you hear the noise in both ears at the same time If sound is to the left of subject, you hear the noise in the left ear earlier and louder than the right ear -ITD: Interaural Time Difference For frequencies below 800HZ The delay between a sound reaches one ear before the other limitation: cone of confusion -ILD: Interaural Level Difference The difference in amplitude arriving in both ears NOT reliable for low frequency sounds -ITD & ILD: Help us locate the azymuth of sound but not pinpoint the location of sound -frequency depends on distance, the further you are the larger the ITD and smaller the ILD

What is a face space and how is it used in the study of face perception> What does the center of the face space correspond to? What does the distance between two points in face space correspond to?

-Face spaces are helpful because they represent each physical feature used in face recognition on a graph. Similar features are mapped closer together, while typical faces are plotted towards the center. We are able to store 5,000 faces because we have some type of dimensional space that we represent neurally and each face is a point on that particular dimension. Similarity between faces is important; we avoid recognizing one person for another; when two points close on dimension space our brain says they are similar and allocate more resources to identify between -A face space is an attempt to map faces on a 3D grid based on different facial features, each of which maps to a different dimension on the graph. -Points closer to center more typical/average and are remembered easier (we are masters of the typical face), edges are more distinct. -Points farther apart are less similar.

Define loudness, pitch, and timbre and explain how each of these auditory qualities relate to physical properties of a sound wave.

-Frequency: (Pitch) Measured in Hz, the number of cycles between changes in pressure per second. -Amplitude: (loudness) the levels of pressure change, in dB. -Timbre: (quality of tone) the qualitative and tonal elements of a sound.

Describe other different types of synesthesia. How does synesthesia differ from visual imagery> What are some ways in which we all have synesthesia- like perceptions? (recall Keke and Bouba)

-Graphemes -> colors; numerical sequences -> spatial arrangements; musical notes -> colors; words -> tastes; It is percieved but not actually there and it is specific to the person; ways in which we all have synesthesia: Language often uses one modality to describe another (sharp knife); Keke Bouba: It suggests a universal synethesthetic phenomenon where people associate sharp sound (Keke) with sharper images (pointed angle) and softer sounds rounded vowels like Bouba we associate it with a round shape; sound with harsh stops in air flow are sharp; happens in every langauge

What is grapheme- color synesthesia? What are some measures to determine whether someone has grapheme- color synesthesia? What role does learning have in grapheme- color synesthesia?

-Graphemes= Colors -A person is said to have synesthesia when their perception of a physical stimulus, such as this black letter 'A', automatically produces an impression which is not ordinarily derived from the stimulus, for example that this 'A' is red. -Color matching-Participants adjust a color (e.g. with 3 knobs, or picking from a color wheel) to match each grapheme-Repeat within and across sessions-Test reliability (within and across sessions); For the majority of synesthetes, learned sequences dominate as the inducing stimuli

What is apparent motion? How is attention involved in the perception of apparent motion?

-Has to do with perception of motion caused by a sequence of static images and that's how people perceive motion; easy to create situations of ambiguity

Describe how the shape of the cornea and the eyeball can determine whether you are near sighted or far sighted.

-In order to see far away objects, the lens has to flatten. Myopia happens when the cornea is too curved for the eyeball, causing the lens to be unable to flatten enough to see far away objects. Or when the eyeball is too long. The light gets focused before it hits the eye causing the image to be fuzzy. -Lens flexibility gets harder as we age, and the near point gets farther and farther—presbyopia (no longer being able to contract lens because lens hardens); light gets focused too far

What are some functions of the outer ear (pinna) in audition? What are functions of the middle ear. Describe how the cochlea responds to high and low frequency sounds.

-Inner ear: Transduces the vibration into electrical signals in the auditory nerve via bending of hair cells; codes perceptual properties of a sound stimulus --Outer ear, what sticks out -Pinna & auditory canal Focuses & amplifies sound waves Helps determine location and distance of sound source -Auditory canal & its wax helps to protect the tympanic membrane (eardrum), and helps keep these structures in the middle ear at a relatively constant temperature

What is lucid dreaming? What are some strategies to increase your chances of having lucid dreams?

-Lucid dreams: Dreaming while being aware that you are dreaming. -Checking watch in dream; waking up for 30 mins in middle of night then going back to sleep; saying i will lucid dream over and over as you fall asleep; practicing counting your fingers during day and you will be able to do it in your dreams

Discuss some ways in which perception becomes tuned or optimized to our experience. You may use examples from auditory perception, face recognition, or other perceptual domains.

-One example of this is the Fusiform Face Area. It is an area in the brain that specialize in facial recognition through the storing of individual features on a "face space". - Another Example of this is harmonics. Harmonics are multiple of fundamental frequency that can be heard with a trained ear - One last example refers to how we see color. Our cones correspond to wavelength which correspond to color. There are three types of cones correpsonding to the wave lengths of red- green, blue- yellow, black- white. They are tuned to the processing of colors. -Laslty, we have motion detertors and hypercomplex V1 cells. (percieves a specific type of motion going in one direction.

How do hallucinations differ from visual imagery? Describe the causes and experience of Charles Bonnet syndrome.

-Perception in the absence of stimuus which has qualities of real perception, including vividness and external location -Different from □ Dreaming (during sleep) □ Illusions (distorted perception) □ Visual imagery (voluntary and less vivid -Charles Bonnet Syndrome □ Affects otherwise mentally healthy people whove experienced significant visual loss due to macular generation. After significant amount of time people will hallucinate sensory experience related to the sense they have lost

Give examples of pictorial, motion- based, and binocular cues of depth.

-Pictoral: Occlusion, relative height, relative size, perspective convergence, familiar size, atmospheric perspective, texture gradient, shadows - Motion: Motion parallax (we perceive objects moving faster if they are near us), deletion (the gradual disappearance of an object moving behind another object), and accretion (the gradual reappearance of an object coming out from behind another object) -

We examined many types of perceptual adaption, including color, motion, and face adaption. What do you think are some of the functions of adaption?

Adaption is important because we have ceratin sensory, receptors, and areas of our body that are tuned to recognize important stimulus in our environment. for example, we have receptors that specialize in faces and the more they adapt the better we recognize a face. Being able to quickly and efficiently recognize color, faces, sounds, odors etc. keeps humans out of danger and aware of their environment.

What is used more in reference frames (head reference and prefered orientation of screen) egocentric (head, retinal, head body) or environment (environment, gravitation)?

Both ENV and EGO are used in reference frames for preference of screen to head orientation, but EGO has a large effect compared to a moderate effect of env

Describe examples of bottom- up and top- down factors that influence our eye movements. Are our eye movements automatic or under voluntary control?

Bottom up cues: salient aspeccts of a visual image attract attention (color, texture); Top down: Prior knoewldge and current goals can over ride bottom up processes; -We can direct an eye movement in under 150ms in response to a task.•For some categories (e.g. faces), people show reliable saccades as early as 100ms!•However, a bias to look at faces overrides voluntary eye movements to other targets.

What are bottom-up and top- down cues that affect flavor perception? Describe how flavor is affected if olfaction does not take place when tasting a substance.

Bottom up cues: texture; which of the 5 basic tastes it is Top down cues; smell, how it smells (olfacation); what you think it is/ already known information about how it tastes. Without olifacation tastes are muted.

Discus two pieces of evidence that we can fixate somewhere, but visually attend somewhere else.

Fixating but attending elsewhere When we stare at a fixation cross between two images but our eyes begin to be distracted by what's on either side of the cross (creating distortions to the images) When we are focussed on one part of the scene but attending to other parts as well, for example focussing on shooting a basketball while trying to see where someone who is trying to block you is.

Describe an example of flicker change blindness, and example of gradual change blindness. What does change blindness suggest about short term visual memory?

Flicker change blindness - when presented with an image (like of a forest) and subsequently a blank screen, and then the same image again but with a slight alteration (a tree being removed from the previous shot) the alteration is almost invisible, and usually goes unnoticed if it's not being searched for. If there's no blank screen between the images, the alteration is extremely distinguishable because there is an instant contrast. Gradual change blindness can occur when a scene changes slightly as you stare, and goes unnoticed, as with what happened when we stared at the boat that changed colors and it was unrecognizable to most until pointed out. These phenomena suggest that our visual short term memory is extremely weak to the adaptation that can happen with our visual processing, and that we're not paying extremely close attention to each part of the scene.

Explain the hard problem of consciousness and the unique problem that subjectivity poses for a science of consciousness.

Hard problem of consciousness- Consciousness can't be localized to one part of the brain, we can observe what parts are active during perceptual and behavioral phenomena but we can't say where in the brain someone is "themselves" On top of that each person's experience of consciousness is entirely unique and that's extremely difficult to quantify, as well as there being information that people have access to but not being consciously aware that they do, making seven harder to study and observe.

What are hypnagogic and hypnopompic states?

Hypnagogic: entering sleep; hypnopompic stages (exiting sleep): stages where people often report visual hallucinations (lines and geometric patterns,phosphenes, form constants) or auditory hallucination (loud noises, crashes and bangs, voices, hearing ones name)

What is a Riechardt detector in motion processing? What are motion after effects?

Motion aftereffects- Motion aftereffects are perceived when the cells on our retinas responding to motion have adjusted to constant motion and then that motion stops, the aftereffect will appear going the opposite direction of the motion and much slower than the rate that it was originally moving.; Riechardt detector: Reichardt Detectors are hypothetical neural circuits postuated for how the brain can track motion. In a Reichard detector, a cell in the brain receives input from two receptors in the eye, call them A and B. The input from A is delayed. If the motion from A to B receptors is timed in such a way that the cell in the brain recieves the inputs from both A and B at the same time then the cell in the brain will fire.

In speech perception, are there clear auditory cues that parse the incoming sounds into words?

No When we look at the speech signal, we see that the acoustic signal is continuous, with either no physical breaks in the signal or breaks that don't necessarily correspond to the breaks we perceive between words

Describe the main limitation with paradigms used in the overflow debate (and other consciousness research).

Overflow argument: The phenomenonilogical richness of what is perceptually experienced (Perceptual consciousness) overflows mental information that can be reasoned about, acted on, or reported (congitive access) ; The CA is a small part of the PC; The main limitation is that it is hard to explore experimentally what someone is aware of but can't report; if we only study what people can report,are we emasuring consciousness itself or soginitive processes that come after (netacognition, attention, memory)

How did Kanwisher's 1997 studies demonstrate that FFA responds specifically to faces?

Part 1: Used fMRI; showed participants photos of faces then objects; defined ROI as region as a set of continuous voxels that pass a statistical thershold of activity; Fusiform ROI in 12 subjects Part 2: Measured responses in the ROI to new stimuli; confirmed previous results; rules out results based on low- level image properties and exemplars of a category Part 3: Checked for additional confounding variables; ruled out results based on subordinate category exemplars; what is foucsed on by observer creates response to brain

Describe or sketch examples of the Gestalt laws of perceptual grouping and segmentation.

Proximity: Objects that are close together tend to be grouped together Similarity: Similar objects tend to get grouped together Good connectedness: lines similar in shape and color tend to be seen as one continuous path Pragnaz: we tend to perceive figures/ obejects in its simplest form Common region: selements grouped together in the same region of space are grouped together synchroncy: elements that move together at the same time tend to be grouped together

Describe how ROIs are defined in an FMRI localizer experiment.

ROI as region as a set of continuous voxels that pass a statistical thershold of activity

What are the differences between rods and cones? How do the responses of cones and rods differ from the response of ganglion cells or from the responses of V1 cells? What types of stimuli drive these cells?

Rods are suited for low-light, low detail vision while cones are for high-light, detail, and color vision. Rods are more in the peripheral retina while cones are concentrated in the fovea. More rods than cones. Different convergence ratios. -120:1 ganglion to rods -1:1 cones to ganglion cells

What is the difference between smooth pursuit and saccades?

Smooth pursuit eye movement occurs when we are following an object moving across the scene and our focus follows it. Saccadic eye movements are more common, as our eyes move around rapidly to be able to focus on different parts of the scene quickly and create a more complete picture of it and to attend to more information.

Discuss some perceptual processes that are likely to be universal across people, and some perceptual processes that differ substantially across people.

Some universal perceptual processes are binocular cues, monocular cues, binaural cues, monaural cues; spatial and temporal cues. -Non universal: color perception, the range of frequenicies that people are tuned to, with training you are able to recognize pitch,

What is the relationship between cortical magnification and visual acuity?

The number of rods is exponentially higher than the number of cones and yet the ratio of cones to ganglion cells is 1:1, whereas the ratio of rods to ganglion cells is ~120:1. Similarly, the portion of the retina that is the fovea is very small, and yet the fovea occupies a large region of the V1.

What are the functions of our proprioceptive system? What happens if the proprioceptive is damages? Describe examples of the interaction between our visual and proprioceptive systems.

The propriocceptive system allows us to know the position of our body and limbs. It allows us to keep our balance, move, and walk. If the proprioceptive is damaged patients need to rely on their visual system to be aware of where their limbs are. One example of this the video of the man who had damage to his proprioceptive system. In order to walk he had to be looking at his limbs in order for them to move properly to walk.

We talked in this course about "top-down processes" What are they? Give examples of top- down processes in sensory modalities.

Top down processes that can influence sensory modalities Top down processes are the ways that our expectations can influence our perception of different phenomena. Vision: when you have to identify parts of a scene for a specific reason, for example searching for how to put something together- you are perceiving it differently than if you just observed what was in front of you to take in what it is. A goal in mind influences how you choose to look at what is in front of you. Smell- When told what a certain odor is, it will influence how pleasant people rate it, as we saw in class with the envelopes of one marked body odor and one marked pizza, but them containing the same scent.

Describe examples of how the different sensory processes (vision, audition, olfaction, proprioception) can interact with one another.

Vision: when you have to identify parts of a scene for a specific reason, for example searching for how to put something together- you are perceiving it differently than if you just observed what was in front of you to take in what it is. A goal in mind influences how you choose to look at what is in front of you. Smell- When told what a certain odor is, it will influence how pleasant people rate it, as we saw in class with the envelopes of one marked body odor and one marked pizza, but them containing the same scent. Taste- How what we're tasting appears and smells as well as what we think it will taste like all influence how we perceive the flavor of a food. Touch- Visual cues, as well as our expectations of how what we're going to touch feels change our perception of touching something. For example- being scared of needles makes getting shots far more stressful than if not. Hearing- the sound that we expect to be hearing will have an effect on what we report to have heard, an example being the mcgurk effect. When different lip movements are matched with the same sound, it is perceived as different sounds.

Give two examples of visual cues that affect audition, and two examples of auditory cues that affect vision. Why is it said that vision generally dominates other senses.

Visual cues effect audition:McGurk Effect: You see a man making a movement with his moth that makes what he is saying indistinguishable. If you don't look at his movements you can hear the sound clearly. (gagaga--> papa) Ventriloquist Effect: You think sound is coming from dummy when your localization cues tell you differently Auditory cues effecting vision: Motion dot bounce example Two balls travelling in opposite diagonal directions (X formation) With "click" noise, people think they bounce off each other Without "click" noise, people see balls as crossing paths In class ball rolling demo Ball rolling against flat plane, Plane has a depth cue With no sound, ball appears to be rolling forward and backwards but with sound it apears to be bouncing Illusory apparent motion

Discuss evidence that visual imagery can be spatial rather just symbolic or abstract.

When people are asked to imagine an object and then identify different parts of the object and how they look, the fact that the response isn't instantaneous about each part of the mental picture means that time to scan across the image we have in our mind. This would be evidence that the image we have in our mind is complete in some way and can be inspected and modified in our imagination. One task where this is observed is when people are asked to identify whether two shapes are the same, and they have to mentally rotate one to match the other to verify. This takes time to try and imagine flipping the shape around to different orientations.

What is face adaption? Give two examples of face adaption. How long do the face adaption effects last? Can you adapt to different faces at the same time? What are some similarities and differences between face adaption and color adaption? Why is face adaption considered a high-level process?

When we are exposed to a slightly distorted face for an extended period, we begin to perceive that as the normal face. This happens because our expectations of the face change as we observe the distorted one longer, which creates the top down perception effect of it appearing normal. One example of this is when in class we observed the grid of faces, normal in the middle and increments of distortion across the x and y axes of the face. When exposed to one of the distorted faces for a while we ended up experiencing this effect.

Why FMRI studies usually present images in long blocks separated by long periods of fixation?

You have to present images for a longer amount of time when looking for what regions of the brain are active in an fmri because it is measuring the oxygenation of the blood, and it takes a while for blood to circulate to the areas of the brain that are activated by what is presented. By presenting stimuli for longer amounts of time, oxygenated areas are able to be distinguished.

What is binocular rivalry? How does it differ from stereopsis?

a. Binocular rivalry occurs when one eye sees a different image than the other eye. Instead of combining the two images, the eyes alternate between focusing on each object, so for a few moments one eye will focus on its respective object, and then the other eye will focus on its object. When transitioning between objects, for a brief period one will perceive a melding of the two objects. b. -Stereopsis:images fuse to produce one image -binocular rivalry: two images competing

Describe demonstrations of studies that support the opponent process and trichromatic theories of color vision.

a. The opponent-process theory states that color vision is caused by opposing responses generated by blue and yellow and by red and green. One experiment is to look at a square with four portions and each of the portion a different color (green red blue and yellow) after staring at it for 30 seconds if you look at the square if it was all white the green would turn to red the red part would turn to green the blue part would turn to yellow and the yellow section would turn blue b. Participants told to combine colors and given three knobs, two knobs, and four knobs corresponding to wavelength. Trichromats only needed three knobs and dichromats only need two knobs.

What does it mean that the auditory cortex is tonotopic?

tonotopic organization refers to the organization of the cochlea. Low frequency sounds are transduced at the apex of the cochlea while high frequences are transduced into electrical signals via the bending of hairs at the basal end.

What is virtual reality? What are some technological requirements for VR to work? What is meant by presence in VR, and what factors increase it? What are some current limitations of VR?

○ The computer generated simulation of a 3d image or environment that can be interacted with in a seemingly real or physical way by a person using special electronic equipment -You need to have a high powered computer; low latency (5 ms) (the time it takes for reality to adjust when moving) to simulate effect of reality -Very low latency between head motion and screen update - In VR every degree of motion made with head forces the screen to constantly update the image that is seen (happens in 5 ms) - If contstraints not met the feeling of presence doesn't happen (sensation that you are in another place from where your body actually is)